The invention relates to methods of treating carboniferous blanks which are impregnated with materials tending to release harmful substances in the course of treatment, and more particularly to improvements in a method of tempering carbon-containing blanks which are impregnated with carbonaceous materials tending to release hydrocarbons, sulfur-containing gases and/or other harmful substances in the course of treatment of blanks in a sealed autoclave.
It is well known to produce fireproof bricks, graphite electrodes and like commodities by tempering in an autoclave suitable carbon-containing blanks which are impregnated with pitch or other carboniferous material. The tempering involves heating the blanks in the autoclave which, in turn, induces the impregnating material to release hydrocarbons, sulphur and/or other harmful substances at normal pressure (approximately 10.sup.5 Pascal) as soon as the temperature rises above a threshold value of approximately 300.degree. C. The treatment in the autoclave involves introducing the blanks into the autoclave, sealing the autoclave, admitting into the autoclave a process gas, heating the interior of the autoclave to tempering temperature, and cooling the tempered products. Heretofore known methods are not entirely satisfactory because it is difficult, if not impossible, to intercept all harmful substances which are released by the impregnating material as a result of heating to and above the threshold temperature which is below the tempering temperature.
A method of continuously converting carbon blanks into graphite electrodes is disclosed in commonly owned U.S Pat. No. 4,942,002.